This invention relates to electrical connecting devices and, more particularly, to electrical connectors which are inserted into cigar lighter sockets in automobiles.
Generally, a cigar lighter plug is inserted into a cigar lighter socket mounted in a motor vehicle (hereinafter called "Socket") wherein the plug permits tapping off electrical power from the electrical terminals in the Socket in order to supply electrical power to accessories in the motor vehicle, such as lighting devices, calculators, shavers and the like.
Such plugs are in various forms such as shown, for example, in U.S. Pat. No. 4,322,122 and U.S. Pat. No. 4,988,315. The plugs in these patents are adapted to fit into a single diameter socket. Different countries have adopted different standardized socket sizes for cars manufactured therein. Therefore, cigar lighter plugs (hereinafter called "Plug") must be designed to fit the Sockets in which they are to be inserted.
Sockets in European cars are larger in diameter than those in U.S. and Japanese cars. If one attempts to insert a large size Plug adapted for European cars into a small size Socket of a U.S. or Japanese car, an arcuate spring contact projecting from the periphery of the Plug body is deformed. If a plug with spring contacts thus deformed is inserted into a large diameter Socket, the poor mechanical fit results in high electrical contact resistance. If a small size Plug is inserted into a large size Socket, inadequate retention is produced, and high electrical contact resistance results.
For the above reasons, Plugs designed for some countries, cannot be used Sockets in from another country. Thus, in view of the foregoing, a need exists for a universal cigar lighter plug which can be used in vehicles from any country in the world.
Japanese Utility Model Examined Publication 4-46387, laid open Nov. 22, 1989, discloses a cigar lighter plug having an arcuate leaf spring held on the plug by a bolt. After loosening the bolt, the leaf spring can be rotated into one of two positions. Once the leaf spring is in the selected position, the bolt is tightened to retain the leaf spring in that position. In one position, the leaf spring extends into the cigar lighter socket, thereby increasing the effective diameter of the plug for fitting a large size socket. In the second position, the leaf spring is rotated to face outward from the contact end, whereby the leaf spring remains outside the socket, thereby permitting fitting the plug into a small size socket. It is considered inconvenient for a user to find tools, loosen a bolt, rotate the leaf spring and then tighten the bolt to adapt the cigar lighter plug to small and large size sockets. If an attempt is made to insert such a plug, adjusted to fit a large size socket, into a small size socket, the leaf spring is deformed or damaged in the same manner as is the contact of the large size plug forced into a small size socket. The inconvenience and difficulty of performing the adjustment of the leaf spring (finding tools, and loosening a bolt which may be frozen in place from use) makes it unlikely that a plug, adjusted to fit a large size socket, will be readjusted to fit it into a small size socket.
The above problem is far from trivial since such a cigar lighter plug is generally used to power portable equipment which is generally designed to be carried from vehicle to vehicle. Thus, adjustment on a daily basis, perhaps oftener, may be required.